Uncoupling of Spinach Thylakoids by Gramine

Gramine and related alkaloids isolated from fodder plants in the Gramineae, Leguminoseae and other plant families [1] are responsible for the toxicity observed in ruminants grazing on these plants [2, 3]. Recently, these alkaloids were reported as toxic to aphids feeding on graminaceous crops [4]. Toxicity of gramine has been related to the known physiological effects of tryptamine related compounds [5]. However, a report on the effects of gramine on energy metabolism of mitochondria [6], provided an alternate mechanism to its toxic action. Further insight into the nature of these effects can be gained through a study of the effects of gramine on energy transduction in thylakoids. We herein report such study. This type of study has been used to assess the importance as allelochemicals of other indol and peptide alkaloids [7-9].